Abhay Satoskar still remembers the first time he held a slide bearing the Leishmania parasite under a microscope—its ghostly form coiled inside immune cells, the silent beginning of a disease that disfigures and destabilizes lives across the tropics. Now, two decades after that moment, his team is on the verge of a breakthrough: the first-ever human trial of a leishmaniasis vaccine, a live-attenuated candidate refined with CRISPR gene-editing technology. The trial, set to launch in Kenya, Brazil, and possibly Cincinnati, marks a turning point for a disease that infects up to 1 million people annually and threatens up to 1 billion across 99 countries—including the United States, where cases are rising.
Leishmaniasis, caused by parasites transmitted through sand fly bites, manifests most commonly as cutaneous leishmaniasis (CL), which leaves lasting skin ulcers and scars. Despite its global burden, the disease has long been neglected by pharmaceutical developers. Treatment remains difficult, often toxic, and no licensed vaccine exists—until now. Satoskar, a professor of pathology and microbiology at The Ohio State University College of Medicine, led the development of a vaccine that deletes the centrin gene in Leishmania major, crippling the parasite’s ability to replicate indefinitely while still triggering immunity. This approach modernizes the century-old practice of leishmanization, in which people were deliberately infected to gain lifelong protection—only now, with precision and safety.
The vaccine has already proven safe in animal models, and in late 2023, the U.S. Food and Drug Administration approved its investigational new drug (IND) application, clearing the way for human testing. This milestone is more than bureaucratic—it signals global confidence. "This helps everywhere in the world because once the U.S. FDA gives its approval, it means other regulators know that it has gone through a very thorough review," Satoskar said. The upcoming Phase 1 trial will enroll 75 to 100 healthy volunteers to assess safety and immune response, with particular attention to those previously exposed to the parasite.
Beyond the vaccine, Satoskar’s team is developing a diagnostic skin test akin to the TB test, which could identify individuals already immune to leishmaniasis—critical for tailoring vaccination strategies in endemic areas. If successful, the vaccine could not only prevent disease in vulnerable populations but also serve as a model for combating other neglected tropical diseases using gene-editing tools.
"We refined the concept using modern technology, making a parasite that does not cause clinical disease but allows for induction of immunity," Satoskar said. As climate change expands sand fly habitats and cases emerge in new regions, this vaccine may soon offer protection where it’s needed most—not just in the tropics, but in backyards across the American South.